A bit more thinking and I'd say that Dragon Age 2 sold manly on name too. Also SW:TOR

There are heaps of games over the years which have sold large at thier launch (not all at same level as Diablo 3, which came out in 2012 so is fresh in your mind)

Your statement "I'm starting to think D3 may have been the first observable game that sold on name and name alone." is just very shallow thinking and I'd say is more about your personal views towards large publishers and games company than anything else.

The fact that it had a '3' in the name make me think that they are keen to use the 'Diablo' name in selling their game or else they may have gone with a name like "Tristram"